Identification of Mid- To Final Stage Phyllosoma Larvae of the Genus Panulirus White, 1847 collected in the Ryukyu Archipelago

Abstract

Nucleotide sequence analysis of the mitochondrial COI gene was performed to identify midto final stage phyllosoma larvae of spiny lobsters of the genus Panulirus caught in the south of the Ryukyu Archipelago (northwest Pacific). The identified larvae were subjected to morphological investigation. All 92 larvae caught in May 2003 were late to final stage phyllosomas of P. japonicus, while 174 larvae in November 2004 comprised four species of phyllosoma group 1 (P. femoristriga (n = 1), P. japonicus (4), P. longipes bispinosus (110), and P. l. longipes (7)), one of group 2 (P. penicillatus (43)), and two of group 4 (P. ornatus (8) and P. versicolor (1)). Photo images of representative phyllosoma larvae, substantiated by molecular identification, are presented. Morphological investigation indicated that the ratio between the widths of cephalon and thorax (CT ratio) of the P. japonicus phyllosomas was the smallest, and discrimination of P. japonicus larvae from the other species of the "P. japonicus group" may be possible using the CT ratio combined with the smaller body size. Intraspecific variation was observed in the arrangement of subexopodal spines of P. ornatus and P. versicolor phyllosomas, indicating this character is not diagnostic to separate these two species. RÉSUMÉ L'analyse de la séquence nucléotidique du gène mitochondrial COI a été réalisée afin d'identifier les larves phyllosomes de langoustes du genre Panulirus, aux stades larvaires allant du milieu à la fin du développement, collectées au sud de l'archipel des Ryukyu (Pacifique nord-occidental). Les larves identifiées, ont été soumises à un examen morphologique. Les 92 larves collectées en mai 2003 étaient des phyllosomes du dernier stade de P. japonicus, tandis que les 174 larves de novembre 2004 comprenaient quatre espèces de phyllosomes de groupe 1 (P. femoristriga (n = 1), P. japonicus (4), P. longipes bispinosus (110) et P. l. longipes (7)), une du groupe 2 (P. penicillatus (43)) et deux du groupe 4 (P. ornatus (8) et P. versicolor (1)). Des images photo des larves phyllosomes représentatives, corroborées par l'identification moléculaire, sont présentées. L'analyse morphologique a montré que le rapport entre les largeurs du cephalon et du thorax (rapport CT) des phyllosomes de P. japonicus était le plus bas, et la séparation des larves de P. japonicus des autres espèces du « groupe P. japonicus » peut être faite en utilisant le rapport CT combiné avec la taille plus petite du corps. Une variation intraspécifique a été observée dans l'arrangement des épines subexopodiales des phyllosomes de P. ornatus et de P. versicolor, ce qui indique que ce caractère n'est pas diagnostique pour séparer ces deux espèces.

Distribution and dispersal of the early larval stages of the Japanese spiny lobsterPanulirus japonicusin the East China Sea

“…In the Kuroshio Current, southwest of Kyusyu Island, concentrations of the final stage (X) larvae were observed and sub-samples were identified as P. japonicus exactly after metamorphosis to the puerulus stage in the laboratory (Yoshimura et al 1999). Chow et al (2006b) supported the hypothesis that the main distribution area of P. japonicus larvae is in the Pacific Ocean as proposed in previous studies (Sekiguchi 1985;Yoshimura et al 1999;Inoue & Sekiguchi 2001;Sekiguchi & Inoue 2002), based on molecular larval identification.…”

“…Because earlystage (I-III) P. cygnus undergo a diurnal vertical migration between the surface and approximately 100 m depth (Rimmer & Phillips 1979), and high densities of P. japonicus phyllosoma were obtained by the IKMT horizontal tows at 35 and 40 m depth in 1998 and 1999, respectively, in the present study, the surface current information shallower than 15 m depth is insufficient to estimate larval transport. However, the archival Argos buoy data and the drift card/bottle experiment in the East China Sea near Kyusyu Island during the spawning season of P. japonicus suggest the possibility that larval transport from the East China Sea to the Pacific Ocean, which has been considered a main distribution area of middle-and late-stage larvae (Sekiguchi & Inoue 2002;Yoshimura et al 2002;Chow et al 2006b), is probably higher in the area south of approximately 32-33°N off western Kyusyu Island. Morinaga (2004) observed two patterns of northward expansion of warm water in the eastern East China Sea that originated in the north front of the Kuroshio Current, southwest of Kyusyu Island.…”

Genetic Isolation between the Western and Eastern Pacific Populations of Pronghorn Spiny Lobster Panulirus penicillatus

“…a/Chow et al, (2006) [10].b/parenthesis indicates number of Panulirus penicillatus larvae morphologically determined.…”

“…In January 2008, a large number of phyllosoma larvae of the genus Panulirus were captured during a research cruise by RV Kaiyo Maru (Fisheries Agency of Japan) operated in the Eastern Pacific. Two morphologically distinct types of phyllosoma were observed in the samples, one of which was identified to be P. penicillatus , since the larvae of this species at mid-to final stages of development are distinct in size and shape from those of the other congeneric species [7], [10]. We initially determined partial nucleotide sequence of the mtDNA cytochrome oxidase I (COI) of some of these Eastern Pacific phyllosoma larvae of P. penicillatus , and observed several nucleotides diagnostically different from those of the Western Pacific previously reported [10], [11].…”

“…Two morphologically distinct types of phyllosoma were observed in the samples, one of which was identified to be P. penicillatus , since the larvae of this species at mid-to final stages of development are distinct in size and shape from those of the other congeneric species [7], [10]. We initially determined partial nucleotide sequence of the mtDNA cytochrome oxidase I (COI) of some of these Eastern Pacific phyllosoma larvae of P. penicillatus , and observed several nucleotides diagnostically different from those of the Western Pacific previously reported [10], [11]. Consequently, we collected and analyzed adults and phyllosoma larvae from other localities covering the entire Pacific Ocean to determine whether there was molecular genetic evidence that the Eastern Pacific pronghorn spiny lobster population is completely isolated from the Central and Western Pacific populations.…”